First things first. David Quammen is a master story-teller, and Spillover (even if weakly-titled) is very well written. Moreover, it is hard to argue with its central premises - that zoonoses (diseases that humans acquire from animals) crop up all the time, that in an era of jet travel the pathogens that cause zoonoses find it far easier than before to spread around the world, and that among them might be "The Big One" - the pathogen that causes a killer pandemic that cuts a horrible swathe through the world's population.

This book follows on from others such as The Coming Plague, that very readable (although lamentably error-strewn) 1994 tome from Laurie Garrett, who some years later graduated from being a "Newsday" reporter to a Council for Foreign Relations fellow convening conferences on AIDS.

What interests me most in Spillover is the chapter on the origin of AIDS that takes up almost the last quarter of the book. And here we see that Quammen (like others before him) has apparently been seduced by the people who promote the "bushmeat" or "cut hunter" theory, which has over the last ten years become pretty much the official explanation for how AIDS came into being. There are many reasons for doubting this version of events[for a few of them, see below],but Quammen swallows all of them whole.

This leads to some major blunders. In particular, Quammen concludes Spillover by trying to bring to life the rather far-fetched hypothesis that is required to allow the "cut hunter" or "bushmeat" scenario of origin of AIDS to be true. I applaud the effort, because for the last 10 years I've been challenging the bushmeat believers to try to put some flesh on their hypothesis. Now that Quammen has done exactly this, it's apparent that the creature he's created is a strange and fantastical one indeed.

Quammen tells the story in tandem with his own recent safari, taken along the same route that, he states, the virus took 100 years earlier. As he puts it: "For me...this journey was all about the cut hunter hypothesis. I wanted to see the route HIV-1 had traveled from its source and imagine the nature of its passage." No doubts there, then. This man is gonna tell us the facts!

Quammen ends up telling a complicated story about a Cameroonian man, possibly a Baka (or pygmy), who in 1908 caught a chimpanzee and in the process cut himself, thereby becoming infected with chimpanzee SIV, the virus that is now widely accepted as the immediate ancestor of HIV-1. Later on, this man (who, unlike most Africans,was apparently somewhat accident-prone) was gored to death by an elephant, but not before he had infected at least one of his sexual partners with the chimp virus. A few years later another local man, whom Quammen rather creepily calls "The Voyager", sleeps with this infected woman and acquires the chimp virus. The Voyager then steals a pair of elephant tusks from some pygmies, and in order to sell them he ends up having to travel 600 kilometres down the Sangha and Congo Rivers, and is forced to lie, conceal and commit murder along the way. Eventually he sells one of the tusks in Brazzaville, the capital of French Equatorial Africa, and ends up living there for the rest of his life. One of the "femmes libres" with whom he has sex gets infected with the chimpanzee virus, which has now presumably adapted to humans, and later she crosses the river Congo to Leopoldville in the Belgian Congo (now Kinshasa, DRC). And it was like this, proposes Quammen, that the AIDS pandemic was born in Leopoldville/Kinshasa.

Quammen would doubtless add that he is not saying this is exactly how AIDS began;he is merely showing how it might have happened. But by so doing, he effectively highlights how very silly and far-fetched the story has become.

It is not only I who thinks this. Others, too, have been less than impressed. Even Alice Roberts, who wrote a very favourable review of Spillover in the Observer (London, UK: November 11, 2012), included the following telling paragraph: "Towards the end of the book [Quammen] loses touch with reality and goes off on a fictional flight of fancy about the origin of HIV, mixed up with his own journey along the Congo river. It all gets a bit Apocalypse Now in this diverting but incongruous departure from the unwavering attention to evidence in the rest of the book." Needless to say, I heartily concur with Alice Roberts.

At this point, let me 'fess up and confirm that I am the author of The River [Little Brown/ Penguin UK; 1999/2000], another book which seeks to explain how AIDS had suddenly come into being.The River proposed that AIDS might have emerged as a direct result of an experimental oral polio vaccine that was made in chimpanzee cells, and then administered to nearly a million Africans in the Belgian Congo and Ruanda-Urundi, two Belgian-run territories in central Africa, in the years up to Independence at the start of the 1960s. At the time that The Rivercame out, OPV/AIDS was merely a hypothesis, albeit one that was backed by a wealth of data and circumstantial evidence.

The River received widespread acclaim when it was published, and it intensified a debate that had started with Tom Curtis's pioneering article, "The Origin of AIDS", in 1992. A year after publication of The River I was invited to attend a 2-day meeting of the Royal Society in London, a meeting entitled "Origins of HIV and the AIDS Epidemic." By the time the meeting took place my main scientific supporter, the evolutionary biologist Bill Hamilton (also the mentor of people such as Richard Dawkins), had tragically died, shortly after making a second trip to the Congo to investigate the OPV theory. He had been one of three organisers of the conference, and had been scheduled to speak. But the meeting went ahead, with the surviving organisers staging it in a manner which would only allow one outcome. Seven years after their initial promises to do so, the vaccine-makers finally produced some samples of the vaccine for testing, and three independent labs declared that these samples were free of HIV-1, free of chimpanzee SIV, and free of chimpanzee DNA. The negative results were absolutely correct. They were also completely irrelevant, for these vaccine samples had been made in America and Europe, and were not the same samples of vaccine that were administered in Africa from 1957 to 1960. But on the basis of these spurious tests, and some other highly contentious calculations about the probable age of HIV-1, Professor Robin Weiss, one of the co-organisers, made a concluding speech which declared that the OPV hypothesis was now highly unlikely.

The conference was a huge eye-opener for me. When, prior to the meeting, several elderly doctors were approached by the people who had made the vaccine, many of them apparently back-tracked on what they had said to me previously in taped interviews, and said the exact opposite. A number of them now asserted that they had been quoted out of context, or implied that I had somehow exaggerated or misconstrued what they had said. And a number of them, at the heart of the conspiracy, simply lied through their teeth. These, however, were lies and spins and implications which Modern Medicine could live with, because it meant that Modern Medicine (and some eminent American and European doctors) could claim that they had had nothing to do with the start of the AIDS pandemic.

So when by the end of the meeting Weiss asserted that the OPV theory had been mortally wounded - or words to that effect - most of the journalists present had not been paying close enough attention to spot the sleight of hand. With a few notable exceptions, these reporters had only been there for the press conference, having otherwise been busily involved in the final two days of the Festival of Science organised elsewhere in London by the British Association for the Advancement of Science. The diary clash was, in the minds of some I spoke with, unlikely to have been accidental.

Since the Royal Society meeting, the journals Nature and Science(widely described as the bastions of science, but in this instance more like the Special Branch of science), have refused to publish any further letter or statement from myself or anyone else in the OPV camp. I have been repeatedly misquoted and misrepresented by the bushmeat scientists, and there have been fairly blatant attempts to discredit both me and the OPV hypothesis.

I, meanwhile, have bided my time and continued my researches. On a more proactive front,I have since 2004 decided to place my interim rejoinders to the Bushmeat scientists, including refutations of many of their claims, on my web-site, www.aidsorigins.com. This now carries several dozen essays and blogs. Here I have consistently explained why the bushmeat claims are misleading, often deceitful, and frequently a nonsense. I have received email feedback from thousands of different readers of the site, and the feedback is enthusiastic and well over 99% positive. Perhaps a third of those readers are scientists, but there are also lawyers, policemen, businessmen, social scientists, authors, even a detective. There are also thousands of members of the general public.

So, since September 2000 a combination of overt opposition by Nature and Science, and of covert opposition (which is perhaps better not described here) has ensured that the OPV theory, in many eyes, has been "disproved", or "refuted". Yet in reality, there is not one disproof that stands up. To date, not one single tenet of the OPV theory has been refuted.

A large part of the reason why The River was published in 1999 was that Bill Hamilton urged me to place my findings in the public domain. I wanted to wait a year or two more. But that's not how science works, he told me. You investigate your subject as well as you can. Then you publish something, they come back at you, you reply, there are arguments to and fro...and in the end knowledge moves forward. Not for the first time I've discovered that Bill was absolutely right. The two-day Royal Society meeting was extremely painful to me, not least because I was subjected to all sorts of spin and falsehoods, and was confronted with claims that I knew in my bones to be incorrect. (In some cases, however, it has taken several years before I could prove it.)But it did achieve one hugely important thing. It brought several of the rodents out of the woodwork. My book forced a lot of these witnesses and protagonists to go on the record in a public forum, and many of them perjured themselves in the process.

I have spent the last twelve years since The River continuing the research process, and all I will say for now is that what was hypothesised in 2000 is now proven. The African polio vaccine WAS made locally in Stanleyville in chimpanzee cells and chimpanzee sera, a fact that was a secret back then, as it still is today. But rather a lot of people knew the secret. And when approached in the right way, many of them have, in different ways and to different extents, come clean.

Now let's get back to Spillover. The earliest hard evidence of the existence of HIV-1 dates from 1959 and 1960, for two blood samples dating from those years have been discovered that contain the virus.(The next earliest sample of HIV-1 dates from 1976, nearly 2 decades later, and it comes from elsewhere in the Congo.) As it happens, both of these two early samples come from the city of Leopoldville, now Kinshasa. The genetic sequences from these two samples differ from each other by about 10% - at least in the one part of the genome where they can be compared. And on this basis the bushmeat researchers, who claim that HIV-1 evolves at a constant rate, use a huge computer programme to create a "molecular clock" which, according to them, can back-calculate the date on which HIV-1 must have first existed, after having crossed species from a chimpanzee. Rather grandly, they call this estimated date "The Most Recent Common Ancestor" (TMRCA), and they calculate that it must have fallen in "around 1950" (first try); "1931" (second version) or "1908" (latest version).There is no evidence for any of these dates, even as approximations. If they exist at all, it is only because the bushmeat boyos tell you that they exist.

Their huge theoretical leap ignores a crucial fact: that in patients with HIV-1, more than 90% of the evolution of the virus comes about not through mutation but through the entirely different process of recombination. These two concepts need some explanation. For mutation, imagine a printer skipping as it prints up an article, and producing one or two incorrect letters. For recombination (or "recom"), imagine something far bigger. Imagine that the printed article comes out with pages 6 to 10 at the front, followed by pages 1 to 5. Perhaps the next time recom occurs, a half-paragraph on page 5 and another on page 6are swapped, while half a sentence on page 7 gets dropped to the back of the article. If this happens a few more times, then the overall changes will be dramatically more far-reaching than changes caused by mutations.

So it becomes clearer that the genetic model (the "molecular clock") used by the bushmeat folks for dating the epidemic is simply a false model: it is like using a tyre-gauge to measure wind-speed. The geneticists tend to reply that they can recognise recombination, and that they exclude recombinant samples from their databases before they begin their calculations of TMRCA. To which I reply: that isn't true. Recom may have occurred early in the history of a virus, in which case there would be no guaranteed way to recognise it in the present-day genetic sequences.And if you cannot recognise the recombinant sequence, there is also no sure-fire way to weed recombinants out of your calculations as you attempt to date the TMRCA. And they might answer: why should there by any recombination going on at the beginning of a virus's life anyway? To which I might respond: if two or more of the chimps whose kidneys provided the tissue cultures used to make the African polio vaccines were infected with SIV, then you would almost certainly have viral recombination taking place in those cultures. It would be happening in vivo (in Lindi Camp, 15 kilometres outside Stanleyville, Belgian Congo,where over 500 of these chimps were housed, sometimes in the same pens,in the late 1950s). And it would be happening in vitro (in the Stanleyville lab, where the vaccine was prepared from pooled tissue cultures made from chimpanzee kidneys and chimpanzee sera). The latter type of recom would recur every time a new vaccine batch was made, and would therefore be expected to be dramatic in impact. The fact that you ignore the factor of recombination means that your molecular clock calculations are a complete nonsense. And because you are using a "relaxed molecular clock", and because you use previous rounds of analysis to confirm the latest round of analysis, you never even notice that the dates are self-confirming. I mean: whoever heard of a relaxed clock, for God's sake? There's a clear and visible danger here of creating a clock that tells you whatever time you want it to say.

Quammen, by the way,can't even bring himself to discuss recombination, so he sums it up as follows: "Evolutionary divergence accumulates by mutation at the base-by-base level (other ways too, but they aren't relevant here)..." Quammen might claim that he was just trying to simplify the explanation about how viruses like HIV-1 evolve. But instead he ends up falsifying the explanation, by leaving out recom altogether.

This is really not rocket science. Forget the back calculations, the ridiculous TMRCA data. The only relevant evidence here - the only hard evidence, as distinct from airy-fairy relaxed clock nonsense - is that HIV-1 has been found in two separate samples from adjoining years (1959 and 1960) in a single city, Leopoldville. This happens to be the same city where the experimental OPV was being tested in a non-stop trial from 1958 to 1960. Every child aged below 5 in that city was supposedly vaccinated- and at least some adults too. Altogether, there were over 30 known trials of this vaccine in the Belgian Congo and Ruanda-Urundi in the late 1950s and 1960 - and the vast majority of the earliest known HIV infections and AIDS cases in the world emerged in these same vaccinated villages, towns, and cities a few years later.

The correlation between the vaccine trials and the emergence of HIV-1 is highly significant, meaning that the chances against these findings being a mere coincidence are of the order of a thousand to one.

"But hold on, Hooper", say the bushmeat people, "there's another proof that shows you're wrong. The true ancestor of HIV-1 is the simian immunodeficiency virus (SIV) of common chimpanzees, we agree, but it's not the SIV from the Pan troglodytes schweinfurthii (Pts) subspecies found around Stanleyville, but the SIV from the Pan troglodytes troglodytes subspecies found in Congo Brazzaville, Equatorial Guinea, Central African Republic and, in particular, south-eastern Cameroon, over 1000 kilometres to the west as the crow flies. You, Mr Hooper, have got the wrong subspecies of chimp." Here the bushmeat people are right on one level, but wrong on the level that really matters. I would agree that in general Ptt chimps appear to be infected with an SIV that is roughly 10% closer to HIV-1 than the SIV of the Pts chimps.

However, please note that the south-east Cameroonian chimps that are so beloved by Beatrice Hahn are almost certainly not the true ancestors of HIV/AIDS, whatever she says. That's because the chimp SIV found in south-east Cameroon is only about 85% identical to HIV-1 (a percentage that varies in different parts of the genome). To be convincing, a true ancestor would need to be well over 90% similar...probably nearer 95%. Hahn and her supporters keep very quiet about this, but they have never found the true ancestor of HIV-1; what they have found is merely a chimp virus that is slightly closer genetically to the human pandemic virus than are the other chimp viruses.That doesn't mean that it's the parental strain, for there may well still be other chimps that are infected with a virus that is even closer to HIV-1.

Alternatively (and indeed far more plausibly), there is no single parental virus,at least in the way that the bushmeat proponents visualise it, in which case they are merely chasing fool's gold.In all likelihood, what is more important is to discover the unusual sequence of events that led to the birth of the ancestral HIV-1. And these events (I believe) centre not on Cameroon and Congo-Brazzaville, but instead on Stanleyville in "the other Congo", the Belgian Congo, nowadays the DRC.

Crucially, not all of the 500-odd chimps that were housed at Lindi Camp (the huge and semi-secret chimpanzee camp set up 10 miles outside Stanleyville for the use of the vaccine researchers) were Pts. Of those 500, about 80 were pygmy chimps or bonobos (Pan paniscus, or Pp), and the rest were common chimps (Pan troglodytes). But there is documentary evidence that at least one of the common chimps at Lindi was a Pan troglodytes troglodytes, a Ptt. This was revealed in a series of published papers by one of the research teams that worked there - and the evidence is crucial. For if one can be proved, there may have been many more.

I already have anecdotal evidence (obtained from several different sources) which makes it highly probable that there were several dozens of Ptt chimps at Lindi, which probably includes the very first chimps at the Camp (which, because they were frequently allowed to wander outside, or play in the joint play-pen, must have interacted with many of the other 500 chimps at Lindi Camp). All we can safely say for now is that many dozens of the Lindi chimps MAY have been Ptt chimps, and since we cannot prove otherwise, we have to assume that they were. Moreover, these Ptt might have infected the other chimps (Pts or Pp) with a Ptt-like virus. In short, the wrong subspecies argument falls apart.

At the start of this piece, I mentioned that Laurie Garrett of The Coming Plague ended up as a big cheese at the CFR. And there's a rule here, I think. The physicians and scientists and scientific writers who prosper these days are those who support the idea that there are pathogens out there in the jungles and the steppes and the arctic wastes waiting to get us, and that the best way to counter these nasties is to place our faith in the forces of American and European medicine, and give our best researchers the money they need to track down the viruses and bacteria and rickettsiae, and stomp them out before they have the chance to do the same to us.

These are the very same types of physicians and scientists and scientific writers who support the bushmeat origin of AIDS - and generally these are people who are going to go far; sometimes very far indeed.Some, like Michael Worobey,have been awarded their own laboratories to run. The major laboratory that is investigating the origins of AIDS, that of Beatrice Hahn in Birmingham, Alabama, was recently awarded a $5 million grant from the Gates Foundation. Of course, Bill and Melinda Gates may well be convinced by Professor Hahn's arguments. And the Gateses are not the same as the US government. But there again when this couple direct their philanthropic assistance towards targets that are favoured by the US government, then one could surmise that the latter might become rather more well-disposed towards any companies that might be owned by the Gateses.

In the recent past, there has been a very strong move towards enshrining the bushmeat hypothesis as "truth" in the public domain. Amazingly, Spillover is the fourth book in the last year that has promoted the bushmeat version of events as if it were fact. The other three books were also nicely written, just like Spillover, and yet all of their authors, like foolish trout, have swallowed the bushmeat hypothesis hook, line and sinker.

I have reviewed the other three books on my web-site. They are: The Origins of AIDS by Jacques Pepin [C.U.P.; 2011]; Tinderbox, by Craig Timberg and Daniel Halperin [Penguin USA; 2012]; and The AIDS Conspiracy: Science Fights Back, by Nicoli Nattrass [C.U.P.; 2012].

So together with David Quammen we have five authors, all of them seemingly quite intelligent people, who completely buy into the bushmeat hypothesis, and who present it as if it were a proven fact. Have they simply been persuaded by the brilliant arguments of the bushmeat boyos? Or is there something else going on?

I don't know. But I will say this. When I wrote The River, I did my level best to interview each of the major living protagonists involved in the origins-of-AIDS debate. This amounted to well over 600 interviews, mostly of two hours or more, and about 500 of which were done face-to-face rather than down the phone.

Although the authors of the three aforementioned books (Pepin, Timberg and Halperin, Nattrass) all devote time and several pages to The River, and to claims that I definitely got it wrong, not one of them bothered to contact me at any point - either to challenge my findings, or to ask me questions. However, I have been contacted by someone through my web-site (a lawyer and social scientist) who asked me several questions, to all of which I responded. Later, this man read the first two of these three pro-bushmeat books and contacted the authors of each by email, to ask them one or two simple questions about their dismissal of the OPV hypothesis. His letters to Pepin, Timberg and Halperin (which he later forwarded to me) were courteous and non-confrontational, and in two instances he sent three separate letters, but apparently not one of the authors could be bothered to reply to any of these approaches.It sounds to me as if these authors have a prior agenda, and are persons whose minds were already made up before they wrote their books. It seems that they want everyone else's minds to be made up too, all along the same lines.

I, meanwhile, have to endure the latest round of attempts to discredit me and belittle the OPV hypothesis. I get the impression that David Quammen (a man with "a generous heart" according to the New York Times review of his book) may, at best, have leafed through The River: certainly his only detailed critique of the book referred to a sentence in the prologue.But he has much to offer in the way of vague vitriol, mixed with apparent praise to give the impression of balance. "Hooper's book was massive", Quammen writes, "overwhelmingly detailed, seemingly reasonable, exhausting to plod through, but mesmerising in its claims..." Later in the book, Quammen describes the OPV theory as "notorious" and "highly controversial"; apparently it "seemed plausible", but in fact had been "directly refuted" by Michael Worobey (which is simply untrue).

His descriptions of the bushmeat scientists are rather funny: Worobey is presented as a courageous hero; the vaccine-makers' hired help,Dirk Teuwen, is presented as a go-getting decision-maker; whereas Beatrice Hahn is very close to being an angel. As for me, apparently I have "spent years researching the subject with formidable tenacity (although not always critical good sense)". Quammen writes with all the fearlessness and ferocity of a slightly timid lapdog, and it appears that (just like Pepin, Timberg, Halperin and Nattrass before him) he is simply repeating the words and views of Hahn, Worobey, Koprowski, Plotkin, and the other bushmeat believers and African vaccine-makers. (It has been clear since at least 2005 that the two groups have joined forces...if they were not always together, that is.)

Would I like to meet Mr Quammen and his generous heart and ask them face to face about their grounds for claiming that OPV has been refuted, and for claiming that I lack "critical good sense"? Yes, I guess that I would!

The River is still available second-hand through sites such as Amazon and Bookfinder.com, and there are plans for an ebook edition in the near future. As for my ongoing research work, thanks for asking. It is going well.